Synthesis and Reactivity of (Diiminate)Fe(II) Benzyl Complex

Supplementary Material for Chemical Communications

This journal is © The Royal Society of Chemistry 2002

Supplementary data

General considerations

All compounds are air-sensitive. All syntheses were carried out under a nitrogen atmosphere using standard Schlenk- and drybox-techniques. Solvents were percolated over molsieves 4Å and stored under nitrogen. Deuterated solvents were dried over Na/K alloy (C6D6, THF-d8) or used as received (C6D5Br) and stored under nitrogen.

NMR-spectra were recorded on Varian Inova 500, VXR 300 and Varian Gemini 200 instruments. IR-spectra were recorded on a Mattson 4020 Galaxy FT-IR spectrometer. Elemental analyses were performed by the Microanalytical Department at the university of Groningen. Reported values are the averages of at least two independent determinations.

Anhydrous FeCl2 and the ‘nacnac’ ligand were prepared according to literature procedures.[1],[2]

Preparation of [(nacnac)Fe(CH2Ph)] . 0.5 C5H12

To a stirred solution of -diimine (4.0 g, 9.6 mmol) in THF (30 ml) was added n-BuLi (2.5 M in hexanes) (3.8 ml, 9.6 mmol). The solution was stirred for 30 min. at room temperature. FeCl2 (1.21 g, 9.6 mmol) was added and the resulting yellow suspension was stirred for 18 hrs. PhCH2MgBr (1.43 M in Et2O) (6.7 ml, 9.6 mmol) was added. The solution turned red immediately and was stirred for 4 hrs. at room temperature. THF was evaporated under reduced pressure. Residual THF was removed by suspending the dark residue in pentane (30 ml, 3x) followed by removal of pentane in vacuo. The residue was extracted with pentane (100 ml, 4x). The extract was filtered, concentrated to ca. 75% and stored at –25 ˚C for 48 hrs. to give red crystals. (4.1 g, 71% based on -diimine).

Anal. C36H48N2Fe.0.5C5H12 requires C 76.98, H 9.06, N 4.66, Fe 9.30, found C 77.47, H 9.31, N 4.74, Fe 9.00.

IR (KBr, nujol mull, cm-1) 3057, 3013, 1594(m), 1524(s), 1484(m), 1437, 1318, 1261(s), 1203, 1176, 1099, 1056, 1029, 1021, 992, 934(m), 859(w), 794, 758, 743, 695(m), 579, 521(w), 438(m).

1H NMR (300 MHz, THF-d8, R.T.) δ(Δν½,) 36.3(71), 12.1(35), -19.7(897), -25.0(217), -29.0(291), -43.6(39), -50.4(40), -56.2(166) ppm (Hz).

1H NMR (300 MHz, C6D6, R.T.,) δ(Δν½,) 117.0(742), 55.4(346), 45.2(120), 40.0(2001), -8.7(54), -17.7(102), -44.3(61), -76.3(77), -112.8(707), -119.1(607) ppm (Hz).

Preparation of [(nacnac)Fe][C6H5CH2B(C6H5)3]

To a stirred solution of [(nacnac)Fe(CH2Ph)]. 0.5 C5H12 (500 mg, 0.83 mmol) in pentane (30 ml) was slowly added a solution of B(C6F5)3 (426 mg, 0.83 mmol) in pentane (20 ml). The red solution almost instantaneously turned dark and a precipitate was formed. The precipitate was filtered off and repeatedly washed with pentane (50 ml, 8x). The brown powder was dried in vacuo. (598 mg, 67% based on 1).

Anal. C54H48N2FeBF15 requires C 60.24 H 4.49 N 2.60, found C 60.00, H 4.58 N 2.59.

IR (KBr, nujol mull) 1640(m), 1514(s), 1314, 1276, 1260, 1176, 1082(m), 1058, 1027(w), 979(s), 935(m), 893, 829, 781, 759, 534(w).

1H NMR (300 MHz, THF-d8, R.T.): δ(Δν½,) 21.3(26), 11.7(10), 7.0(71), 6.6(17), 6.5(33), 6.3(18), 4.4(6), 3.5(31), 3.2(7), 2.7(13), 2.4(30), 1.4(18), 1.2(9), 0.8(25), 0.7(19), 0.6(19), 0.4(23) -8.7(134), -17.7(117), -25.2(149), -37.2(26) -38.5(49), -39.7(30), -52.0(94), -55.9(97), -60.2(138), -94.6(299).

19F NMR (188 MHz, THF-d8, R.T.): δ –131.8 (d, JFF=21.45Hz, 6F, o-F), -167.3 (t, JFF =19.66Hz, 3F, p-F), -169.5(m, 6F, m-F).

19F NMR (188 MHz, C6D5Br, R.T.): δ -89.7 (br), -167.3 (br), -169.5 (br, with shoulder 157.7).

VT NMR spectroscopy

19F VT NMR (470 MHz, C6D5Br) spectra were recorded from 253K to 203K with 5K intervals using 20 mg 2 dissolved in 0.5 ml solvent. Reversibility was confirmed by cooling down the same sample.

1H NMR (500 MHz, C6D5Br, 253 K): δ(Δν½,) 68.3(457), 47.2(698), 23.7(67), 22.4(429), 9.1(278), 8.2(294), 7.2(18), 6.9(13), 6.9(17), 4.8(26), 3.4(45), 2.8(29), 1.6(20), 1.1(30), 1.0(49), 0.8(71), 0.7(26), -0.5(122), -3.9(187), -9.2(9374), -11.7(273), -48.8(120), -68.2(166), -73.4(288), -76.2(362).

19F NMR (470 MHz, C6D5Br, 253 K): δ –82.6 (o-F), -128.4 (o-F), -150.7 (m-F), -152.8 (p-F), -161.5 (p-F), -163.4 (m-F).

NMR tube reaction of 2 with THF

To a solution of 2 (20 mg) in C6D5Br (0.5 ml) was added a small drop of THF-d8. The dark brown solution turned bright yellow instantaneously.

19F NMR (188 MHz, C6D5Br/THF-d8, R.T.): δ –129.7 (d, JFF=20.3Hz, 6F, o-F), -163.3 (t, JFF =19.19Hz, 3F, p-F), -165.8(m, 6F, m-F).

References

1

1. Kovacic, P.; Brace, N.O. Inorg. Synth.1960, 6, 172-173.

1. Budzelaar, P.H.M.; Moonen, N.P.; de Gelder, R.; Smits, J.M.M.; Gal, A.W. Eur. J. Inorg. Chem.2000, 754-769.